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Title: STRUCTURED MOLECULAR GAS REVEALS GALACTIC SPIRAL ARMS

Abstract

We explore the development of structures in molecular gas in the Milky Way by applying the analysis of the brightness distribution function and the brightness distribution index (BDI) in the archival data from the Boston University-Five College Radio Astronomy Observatory {sup 13}CO J = 1-0 Galactic Ring Survey. The BDI measures the fractional contribution of spatially confined bright molecular emission over faint emission extended over large areas. This relative quantity is largely independent of the amount of molecular gas and of any conventional, pre-conceived structures, such as cores, clumps, or giant molecular clouds. The structured molecular gas traced by higher BDI is located continuously along the spiral arms in the Milky Way in the longitude-velocity diagram. This clearly indicates that molecular gas changes its structure as it flows through the spiral arms. Although the high-BDI gas generally coincides with H II regions, there is also some high-BDI gas with no/little signature of ongoing star formation. These results support a possible evolutionary sequence in which unstructured, diffuse gas transforms itself into a structured state on encountering the spiral arms, followed by star formation and an eventual return to the unstructured state after the spiral arm passage.

Authors:
 [1];  [2];  [3]
  1. Joint ALMA Office, Alonso de Cordova 3107, Vitacura, Santiago 763-0355 (Chile)
  2. NAOJ Chile Observatory, Joaquin Montero 3000 Oficina 702, Vitacura, Santiago 763-0409 (Chile)
  3. Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)
Publication Date:
OSTI Identifier:
22078456
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 759; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; COSMIC GASES; DIAGRAMS; DISTRIBUTION FUNCTIONS; EMISSION; MILKY WAY; MOLECULES; SPIRAL CONFIGURATION; STARS

Citation Formats

Sawada, Tsuyoshi, Hasegawa, Tetsuo, and Koda, Jin, E-mail: sawada.tsuyoshi@nao.ac.jp. STRUCTURED MOLECULAR GAS REVEALS GALACTIC SPIRAL ARMS. United States: N. p., 2012. Web. doi:10.1088/2041-8205/759/1/L26.
Sawada, Tsuyoshi, Hasegawa, Tetsuo, & Koda, Jin, E-mail: sawada.tsuyoshi@nao.ac.jp. STRUCTURED MOLECULAR GAS REVEALS GALACTIC SPIRAL ARMS. United States. doi:10.1088/2041-8205/759/1/L26.
Sawada, Tsuyoshi, Hasegawa, Tetsuo, and Koda, Jin, E-mail: sawada.tsuyoshi@nao.ac.jp. Thu . "STRUCTURED MOLECULAR GAS REVEALS GALACTIC SPIRAL ARMS". United States. doi:10.1088/2041-8205/759/1/L26.
@article{osti_22078456,
title = {STRUCTURED MOLECULAR GAS REVEALS GALACTIC SPIRAL ARMS},
author = {Sawada, Tsuyoshi and Hasegawa, Tetsuo and Koda, Jin, E-mail: sawada.tsuyoshi@nao.ac.jp},
abstractNote = {We explore the development of structures in molecular gas in the Milky Way by applying the analysis of the brightness distribution function and the brightness distribution index (BDI) in the archival data from the Boston University-Five College Radio Astronomy Observatory {sup 13}CO J = 1-0 Galactic Ring Survey. The BDI measures the fractional contribution of spatially confined bright molecular emission over faint emission extended over large areas. This relative quantity is largely independent of the amount of molecular gas and of any conventional, pre-conceived structures, such as cores, clumps, or giant molecular clouds. The structured molecular gas traced by higher BDI is located continuously along the spiral arms in the Milky Way in the longitude-velocity diagram. This clearly indicates that molecular gas changes its structure as it flows through the spiral arms. Although the high-BDI gas generally coincides with H II regions, there is also some high-BDI gas with no/little signature of ongoing star formation. These results support a possible evolutionary sequence in which unstructured, diffuse gas transforms itself into a structured state on encountering the spiral arms, followed by star formation and an eventual return to the unstructured state after the spiral arm passage.},
doi = {10.1088/2041-8205/759/1/L26},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 759,
place = {United States},
year = {Thu Nov 01 00:00:00 EDT 2012},
month = {Thu Nov 01 00:00:00 EDT 2012}
}